The investigators prospectively enrolled and followed a cohort of 97 teenagers before, and 6, 12, and 18 months after starting depot medroxyprogesterone acetate (DMPA). They examined whether the pattern of early weight gain observed among adolescents initiating contraception with DMPA predicts continued excessive weight gain and evaluated the risk factors for excessive weight gain. The entire study population was categorized into two groups based upon weight gain observed at 6 months; excessive early weight gain was defined as a gain of more than 5% of starting body weight. Excessive early weight gain was seen in 20 patients (21%, mean body mass index [BMI] = 23.3%), and the remainder of the cohort (77 patients, 79%, mean BMI 23.3%, P < 0.01) gained 5% or less of their starting weight. Although no risk factors for early weight gain were identified, excessive early weight gain (> 5%) at 6 months was correlated with a higher BMI at 12 and 18 months. Although the mean BMI was not significantly different between the two groups at baseline (23.4 [< 5% early weight gain] vs 24.5 [> 5%], P = 0.3), and both groups showed an increase in BMI at 12 (24.2 vs 28.7, P < 0.01) and 18 months (25.7 vs. 32.1, P = 0.01), the excessive (> 5%) early weight gain group demonstrated a greater and excessive increase at all time points such that the differences between groups became significant. Furthermore, the mean BMI in the excessive weight gain group moved into the obese range by the end of study. The authors concluded that adolescents who experience more than a 5% weight gain after 6 months of DMPA use are at risk for continued excessive weight gain with continuing use of the method. They suggest that a 6-month checkup be used to identify adolescents at risk for continued excessive weight gain and counsel them about contraceptive options.

Commentary

In the June 2010 issue of OB/GYN Clinical Alert, we discussed the black box warning concerning low bone density and DMPA. The study by Harel et al demonstrated that bone density recovers after discontinuation of use.1 Although theoretical concerns about bone density still occupy the imagination of the FDA and some clinicians, weight gain presents a more pressing concern for most teenagers considering a contraceptive method. With obesity rates continuing to rise in our country, any intervention that increases the risk of weight gain demands serious attention. Weight gain has been reported in more than half of adolescents receiving DMPA and is cited as the primary reason for method discontinuation by more than 41% of adolescents who use the method.2,3 Although prior studies examining risk factors for weight gain among adolescents on DMPA have suggested that African American race and overweight status at initiation predict weight gain, these effects have not been consistent.

The recently published manuscript from Bonny et al represents a secondary analysis of data from a 2-year prospective study of bone density and hormonal contraception.4,5 The study population consisted of post-menarche females aged 12 to 18 years attending one of four urban adolescent health clinics in Cleveland. The current analyses include only those subjects who selected DMPA for contraception. Of note, all of these subjects also participated in a randomized trial evaluating an intervention for unscheduled bleeding and received either adjunctive estradiol cypionate or placebo. It is also important to point out that girls with a body weight that exceeded 250 pounds (this was the upper limit of the DEXA scanner) were excluded from the study.

The authors based the decision to define weight gain in the first 6 months of use as excessive when it exceeded 5% of the baseline weight on findings by Le and colleagues.6 These investigators found in a study of women 16–33 years, those who gained more than 5% of their body weight within 6 months of DMPA initiation were at risk for future weight gain with the method. Although using this criterion, the study cohort in the Bonny paper was not dichotomized until 6 months; there were no significant differences in the baseline characteristics between the groups. In other words, in contrast to prior studies, race (more than 60% were African American), age, physical activity, age, or baseline BMI (more than 35% obese) did not predict weight gain at 6 months. A multivariant analysis confirmed this lack of association.

However, after 6 months of use we can begin to make predications. At this time, a group of users at risk for significant and clinically important weight gain emerges. The screening test is simple; simply weigh your patient and compare the change in weight over 6 months as a percentage of the initial weight. If this exceeds 5%, your patient is at risk for excessive weight gain.

As clinicians, this informs our practice. Since we can't make assumptions about which teens will develop unacceptable weight gain after starting DMPA, the method should be in the portfolio that we discuss with all adolescents that present for contraceptive counseling. DMPA is a highly effective and well-tolerated, reversible method. Unfortunately, rates of discontinuation are high (DMPA is not a true LARC [long-acting reversible contraceptive] method because of this), and this can expose young women to the risk of unintended pregnancy. Concerns about weight gain and other side effects can prevent an adolescent from returning for a repeat injection. But the data suggest that this should not be a worry for most users of the method. Almost 80% of the population in the Bonny study did not experience excessive weight gain at 6 months.

Discussing this issue up front with your teen patients could be a mechanism for improved compliance and success with the method. Having a clinician visit at the time of the third shot specifically to address side effects and measure weight gain would be highly informative and could direct management. Those girls who have gained less than 5% of body weight should be given good dietary advice (avoid the Big Mac and sugar soft drinks) and reassured that their contraceptive method will have little impact on body weight. On the other hand, while girls who gain more than 5% should also receive a health promotion message, they also should be advised that continuing DMPA is likely to result in continued weight gain and will increase their risk of obesity. Alternative LARC methods should be recommended.